One problem with page processing systems, including copiers, printers, scanners, data capture and other systems, relates to the identification of individual pages and discrimination between different pages which are handled by the systems. For example, it would be useful in these types of systems to have the capability of uniquely identifying paper being processed as being a particular page, or a particular type of form. With such capability, data processing systems could process information entered on forms, using optical character recognition for example, to automatically identify and process many different types of forms despite varying locations of data fields depending on the type of form. Alternatively, pages following a paper conveyance path could be uniquely identified at different locations along the path. In copiers and other processing systems, identification of form could be utilized to detect originals, e.g., so-called "water mark verification," or to provide enhanced data processing capabilities.
One specific device suitable for automatic page identification is disclosed by U.S. Pat. No. 5,629,499, which relates to a multiple page or form digitizing clipboard; using the clipboard, a user can actually write upon multiple, stacked pages or forms, with a digitizer beneath the pages or forms capturing pen stroke information. Clearly, in such a system, association of pen stroke information with the proper one of the stacked pages or forms is important. In such a system, it would be useful to provide a mechanism for automatically detecting a current page or form being written upon, e.g., by using a mechanism which electronically "fingerprints" the page or form, and for then automatically discriminating between the different pages or forms in use.
Some prior systems do propose automatic systems for identifying pages, for example, by relying upon specially-positioned codes or marks for identifying forms or pages, which can be manually scanned by the systems themselves. However, systems of this type require the use of special forms (having the codes or marks preprinted on the page or form), as well as alignment or scanning procedures for measuring the codes or patterns; these systems generally are directed to special applications and cannot be readily used with a wide variety of applications. It would be useful to have a system that can automatically identify a page or form based on the inherent characteristics of the page or form, and which does not require specially formatted forms or code alignment procedures. Unfortunately, systems for page identification based on inherent characteristics are typically limited by difficulties in normalizing measurements, for example, by adjusting for discrepancies in ambient light, and variances in measurement distance and angle.
A definite need exists for a page identification system which can detect and differentiate pages based upon their optical characteristics. Ideally, such a system should be low-cost, adaptable to a wide variety of page processing systems (such as copiers, scanners, printers and other data processing systems), and should provide for a high degree of reliability. The present invention solves these needs and provides further, related advantages.